Heavy-duty flexible drill pipe



July 18, 1950 .1. A. ZUBLIN 2,515,366

HEAVY-DUTY FLEXIBLE DRILL PIPE Filed May 4, 1948 2 Sheets-Sheet 1 INVENTOR.

July 18, 1950 J. A. ZUBLIN 2,515,366

' HEAVY-DUTY FLEXIBLE DRILL PIPE I Filed May 4, 1948 2 Sheets-Sheet 2 IN VEN TOR.

tfa n llablip Patented July 18, 1950 {UNITED EFPATE-NT OFF ICE HEAVY-DU'1Y FLEXIBLE DRILL PIPE -:J.0hn A..-Zublin, LosAngeles flalif, ""Application May 4, 1948; Serial No.-25,037

ClaimS. 1

In my cope'ndingl; i application serial No. 7383335., file'd1 March 31, 1947,. entitled .fliflexible DrilLPipe, I have -described;and claimed a a fiexible drill pipe havingea generally helical slot in the wall-thereof which imparts flexibility to the drill. pipe. According toltheudisclosure of that application,-theoppcsed=edges of the'sloti-are provided with complementary iteethixwhich interengagefor the purpose of: preventing excessive distort-ion ofczthe pipe'l The present-application 1 -relates to an invention which embodies-some of -theprinciples of-the above-mentioned applica- -*-tion; but the present application discloses addiional and improved structures-which -arei paricularly useful fo'r drillinglateral bores deviating rom e xisting well bores-and-for side wall coring In -one-form of=the invention-disclosed inmy uabove-mentioned application Serial- No: 738,335, --the oppo'sed edges or theslot are provided "with nterengaging' an'd loosely interlocking teeth of com-plementary= dove tail configtitationi' The ---teeth of this-configuration preventexcessive distortion of the tubular'--member; -irrespective of whether the stresses-applied to' thelmember tend to=-caus "'elong ation;-* -bending or twisting? '-The "form of the i-nvntion illustrated in that applica- :tion is satisfactory when=-thestresses arenot i so great astocausethe tubular-member to distort to sucham'extent that the teetl-i disengage as a"-result of--radia=l displacement relative to each other' when the interlocking I teeth disengage as a -rsulfi of' 'relative radial =displacement=,-the I ubular member is likely to-telescope upon-itself when subjected to compressionstresses;- bending "---stresses,= or torque-stresses. I-he- -tu-bular =mem- -beris' also -likely tobecome'-'elongated--andto 'cquirea permanent set when tensile stresses are "----'=-appliedto -the-*memberwhiletha -teeth are' -disengaged-J it-has beenfoundthat -a tubular -mem-" -berconstructed in-acccrdance -with theteachings of -the aboveapplication cannot be expec'tedto a: ssume acurVature' With a' radius of 'less-than about eight times the diameter: o'f the tiibular member without permanent injury to the-=-mem 'tr The flexibility otisucha tubular member tcould lie-increased bysreducingitheapitch ofztheahelical slot, but:lrhaveiioundvthat tooigreatza reduction 1:: in the :pitch fisi impractical: because-ethecmember- 2 l5 be. v:d,one w..on1y,: with at sacrifice in the ultimate .yzistrength. of the Jmemben: It will-zalso be tapparent. that if the-wall of thetu'bular .member is ,i .reduced in thickness there will bea .greatertend- 5 ency for theiinterlocking teeth to:.-..become;.:.dis-

engaged; whichi-. wiouldr-: lead to the undesirable results discussed above.

One of the uses for such flexib1e tubular:mem numbers in which :I am particularly interested is in connectionwith .the drilling ofizlateralt bores uaedeviating. from the vertical bores of wells such as ;oil -wells.; In. .another' copendingu. application, Serial No. 769,489, filediA'ugust 19,3'1947, entitled Apparatus :iorvzside Wall :Coring, (now. =abandoned), I have describedethe use of such a flexible r.tubular. 1member as the drill stems-for a \bitused for. taking cores from the side .wall of a well. It is difiicult and often impractical toipro- Fvide; fiuidt'circulation around a :side wall coring -bit, and it is-,.:therefore,':often necessary to :resort to dry; cutting of the core. Inztheabsence of fluid circulation, some means must be pr'o'vided forvremoving. thelooseumaterial in the annular space between the coreandthe coreihole. I I The. :present invention overcomes the" disadvantagesand'difiiculties described-above: In ascordance: with the teachings of thepresent-invention a plurality of generally circumferential go-jzslots are cut -through-the wall o1 a tubular'memc :ber. and the'zslots are distributed along 1 the :length 1': of x the: member so :that 'the -member is divided intoa plurality ofr'sectionszz While-:th'e' slots are E; generally circumferential, they, deviate from a :truercircumference in a manner to" form :a: plurality of inter-engaging and looselyinterlocking teeth of' clove-tail-iconfiguratiombThere are a 9.1; v plurality of' such dove-tail teeth on each :end of each section and the interlocking ofnthese teeth limitsr-the extent of-irelative axial movement of the adjacent-sections? The width and direction o'fithe slots, the shape of theteeth and-:the-Ithick- "ness of the wall ofthe-tubular member :arecor- :related in aa'nanner hereinafter described tospreventithe-sections fromsbecomingseparated. j also contemplate the forming= of a-thelical 11": groove; extending around and along the i tubular ;memberiwhenthegmembereis to bezusecl as acdrill tem: for axcoringm'bit;rnTheiihelical. groove; or .-:i rather; atherridgeswlving betweenconvollltionsof 59;,51'18; helical: groove; :serve to a-conveyi theiiloose material out of the annular ;.-spacebetween a E'TCOITB? and-the core: hole. 1' 5 Such an arrangement is n particularly sadvan-tageous; in ;,t;hcse;-=. instances n; where fluid-circulation inthe core; holeisiteifiher Eli impractical or impossible.

The primary object of the present invention is to provide a flexible drill pipe which will assume a curvature with a radius sufiiciently short to make the drill pipe practical for use in drilling bores which deviate laterally from existing well bores. A further object of the invention is to provide a flexible drill pipe which is extremely rugged and which will withstand use in operations which require the drill pipe to withstand tremendous stresses. A stillfurther objector" the invention is to provide a heavy duty drill pipe which is flexible and in which none of the elements of the pipe are required to bend. A'fuF teeth 22 and 23 to limit the relative axial movement to the distance designated b. The arrows in this figure illustrate the forces of action and ther object of the invention is to, reduce the.

likelihood of fatigue failure in flexible drill pipes. Still another object of the invention is to proreaction between the abutting surfaces of the members. Figure 7 illustrates the positions as- 'sumed by adjacent sections when the drill pipe is vide a flexible drill pipe for use in sidewall cor 1,

ing operations in which means are provided on the pipe for conveying loose cuttings from the core hole.

v,Further objects and advantagesv of the invention will be referred to' in the following detailed description of exemplary forms of my invention. The detaileddescription makesreference'to the accompanying drawings wherein:

Figure 1 is a perspective view of a portion of a drill pipe constructed in accordance with one form of the invention;

Figure 2 is a transverse sectional view of the .form of. the invention illustrated in Figure 1, r this view. being taken through. the mid-sections of the interlocking teeth which join adjacent sections of the drill pipe;

Figure 6 is va. diagrammatic view illustrating the relationship between adjacent sections of the drill pipe when subjected to tensile stresses; Figure 7 is a diagrammatic view illustrating the relationship between adjacent sections of the drill pipe when the .drill pipe is subjected to compression;

-Figure 8 is a side elevation view of j a short length of drill pipe provided with a means for conveying loose cuttings from a core hole; and Figure 9 is a view showing a development in a plane of a joint between two sections of drill pipe illustrating amodified shape .for the dovetail-teeth. l .1.

=-I have illustrated in Figure *1 a" portion of a drill pipe consisting of the sections Hi, Hand i2. The section lll'is provided with threads l3 for connection to another length of flexible, drill pipe or to any standard rigid drill pipe; The sections 10 and H are divided by a slot M which extends generally circumferentially about the drill pipe, and which has the configuration shown in the drawing to provide teethzl5, l6 and ll of dove-tail configuration on the-lower end of the section l0 and similar teeth l8, l9 and on the upper end of the section II. The sections I I and I2 and the remaining sections of the drill pipe are connected in the same manner and it will suffice to describe only the joint betweenthe sections In and H.

' Figures 5, 6 and '7 illustrate diagrammatically the manner in which the teeth of dove-tail configuration limit the extent of certain types: of relative movement between adjacent sections of subjected to compressive stresses. The relation ship will be apparent from a mere inspection of this figure in which the arrows designate the forces of action and reaction between the abutting surfaces of the members. i

' 'It will also beapparentfrom an inspection of Figures 6 and 7 that the fiexible'drill pipe will tend to assume a straight configuration when subjected toeither tension or compression. This isan advantage. of my flexible drill pipe because it aids in manipulatingydrill bits on the lower end of drill pipeswhenitis desired to drill a straight bore which deviatesfrom a curved bore. The foregoing reference to- Figures 5, 6 and '7 explains the manner in which the intermeshing teeth of dovetail configuration cooperate to prevent separation of;;th e sections when the drill pipe is subjected to tension, compression or bending. Those figures dornot disclose the manner in which the teeth prevent the sections from becoming separated by relative lateral movement. This cooperation can be best understood-by reference to Figures 2, 3 and-4, Figure ,2 illustrates the-teeth |8,- l9 and," on the section I l.- The teeth I5, 16 and 11 on the section I0 are shown in their normalor neutral positions by full lines. The; dotted line positions in Figure 2, designated by the reference numerals I5; I 6, and ll illustrate the positions-pf the teeth [5, l6 and I! after the section :lllhasbeen moved laterally relative to the sectiorrlL, It will be seen that the edges of the tooth] l abut the adjacent edges of the teeth IS-Yand 20 .whenthe. tooth l! is in the position ll! designated by the dotted lines. It willalso be noted-that one: edge of the tooth l5'abutsthe adjacent, edge of the tooth l8, and that one edge of the tooth l6 abuts'the adjacent edge of the tooth: I8; The extent-of relative lateral movement between the sections is thus eifectively limited so uthat noneof the interlocking teeth of a; joint can become disengaged. Although Figure 2 illustrates relative-lateral movement between thesections l0 and H inonly one direction, it will be apparent'that relative lateral movement in anyothend-irection will be limited in the same mannerandto the same extent.

It will be apparentfrom, an inspection of Figure 2 that the distance ,1 :0 between theqouter corners of onetoothshould'be'greater than the distance y between the adjacent inner corners of adjacent teeth. :1 I have found this to be a conthe wall of the tube;

Six intermeshing teetlifarepresent each joint in the formof tl'ie invention illustrated in Figures 1 and- 2'. greater-number -of "=te'eth wise-the same as th The 's'ections of tubing Will'- ratd byrelative-lateral movement sc 'ilorig as the distance 113' between theouterwear-nerve one cent inner corners Of 'adjaQent' teeth.

a section of rthe drill pipe' and-the-teeth 33-, 34 and; 4

may te emsmyea in-each lmt-mifirnave reund member einr' thatno appreciable ad-vantage is ei ive lliistrated -iri i Fi re 2.

6t bec'om sepa- The slots l4 and 2'4" have-2 bee'rr illustrated as extending in radi'al directions*thi ougl itheawalls of the pipes. *That arrangei-flent is to be preferred because radially extending slotsicanlbe; cut with greater-facility; but it is not n'e'ces'"s'ary as will be apparent from an inspection of Figure 4. The slot is designated bythe reference numeral 29. The teeth 3l-'and 32 are on one are on the other section of-the drill pipex: It will be noted that the slot 29 extends through the wall of the "pipe in such manner that the lateral edges of the tooth' 30 are parallel to each other, the same bein'gtrhe 'of'the teeth 31' and 32.; However, the edges of thetooth 33 converge toward the inner-surface of--.the-wall'of thepipe to a much greater extent than was true' of the 4 teeth formed bytheradial 'slo'ts of Fig-u 3. The edges of the teetlr- 34 and emerg in a manner similar to the edges of the tooth 33. Referring particularly to the tooth 35, it will be seen that the distance :0 between the outer corners of this tooth is greater than the distance y between the adjacent inner corners of the teeth 30 and 32. The same relationship holds true for the teeth 33 and 34, and the sections of the pipe will not separate by relative lateral movement so long as teeth having this relationship are distributed around the circumference of the pipe. It will be seen that the relationship just described is not true with reference to the teeth 30, 3| and 32. The distance between the outer corners of the tooth 30, which distance is designated by the reference character a;'', is less than the distance between the adjacent inner corners of the teeth 33 and 35, which distance is designated by the reference character y".

Figure 9 illustrates a form of dove-tail tooth which may be used instead of the form illustrated in the other figures of the drawings. The slot 36 assumes a path which results in giving portions of the edge of the tooth 31 curvatures which are arcs of a circle having a center at O and a diameter d. Another portion of the edge of the tooth 31 has a curvature which is an arc of a circle having its center at 0 and a diameter D. A portion of the edge of the tooth 38 is an arc of a circle having its center at 0 and a diameter D, while other portions of the edges of this tooth form arcs of a circle having its center at o and a diameter d. The tooth 39 and the additional teeth are of similar configuration. I have found that teeth of the configuration shown in Figure 9 minimize shock and Wear between the sections of the drill pipe.

I prefer to construct my flexible drill pipe by starting with a unitary tubular member and cutting the slots therein. A conventional drill pipe is suitable for use as the initially unitary W maybe-awaits an sui- 5 manner rid-W know-n m th -=havesuccessr uynsew sesametom omewhar high i'itti venttheir iassemblyi' It we'uia be psssime; to

ast'fthe sections in interloeking engagefiiem with ach other in somewhat the maiiner -thalrcliains have been -casti bfit it is'dinlikelwthat iiasthe a'ssembled s tions regret -tubular member Spiralgfioove 41 iefer'ablyjciit onltli 'bi'ilar slots have been cut to divide the tubular member into sections.

The flexibility of my drill pipe can be controlled within limits by selecting appropriate lengths for the sections which make up the drill pipe. A drill pipe which consists of a large number of relatively short sections can assume a curvature having a smaller radius than would be the case with a drill pipe consisting of a lesser number of longer sections. The sections need not be of uniform length throughout the length of the drill pipe and it is possible to produce a drill pipe having a certain flexibility along one portion of its length and greater or lesser flex-- ibility along other portions of its length. The

permissible relative movement between any two joined sections is controlled to a considerable extent by the width of the slot which defines the inter-locking teeth. A slot of greater width permits greater relative movement between the sections. Care must be taken, however, to maintain the relationships discussed above in connection with Figures 2 and 3 or 4.

The foregoing detailed description of exemplary forms of my invention has been given to enable others to understand my invention and to obtain the benefits thereof. However, it is understood that the invention is not limited to the exemplified forms and that various modification-s may be resorted to without departing from the scope of the invention as defined by the following claims.

Having thus described my invention, I claim:

1. A flexible pipe comprising an elongated tubular member subdivided into a plurality of sections of rigid pipe of substantial wall thickness in end to end relationship with a plurality of dovetail teeth and complementary recesses on the cesses and loosely interlocking the teeth of the adjacent sections with appreciable clearance to form a loose joint permitting limited relative movement inany direction between the sections, saidteeth having substantially-fiat end portions lying in planes generally perpendicular to the axis of the pipe at least certain of said recesses having their side edges converging from the outer surface ofthe pipe wall to the inner surface thereofand the side edges of the teeth positioned in such recesses also converging from the outer surface of the pipe to the inner surface thereof, the extent of such convergence being so related to-the thickness of the wall of the pipe and the normal clearance between the teeth and their respective recesses that the tapered edges of any such recess abut the tapered edges of the tooth thereinafter limited radial inward movement of a such tooth, such converging recesses being sufficient in number and so spaced about the circumference. of the pipe as to prevent disengagement of the sections by excessive relative lateral movement in any direction.

three complementary teeth of dove-tail configuration on each side of the slot, the teeth on one sideof the slot intermeshing and loosely interlocking the teeth on the opposite side of the slot to provide a loose joint and to prevent axial separation of the sections, said teeth having sub;

stantially flat end portions lying in planes genegallyperpendicularfto the axis of the pipe to the pip e ,in directions such that at least three K of the teeth around the circumference of the pipe -,-,conve rge width from the outer surface of the ---;'pip e,to he in ner surf ace thereof, the width of the slot'being so related,- to the extent of convergence of the teeth and the thickness of the wall of the pipethatat least one converging tooth W 11abutadjacentedges of adjacent teeth after limitedrelativelateralmovement of the sections Min any-.idirection-to thus prevent lateral separav 1 25 2. A flexible pipe comprising a pipe having a I REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Namev 1 Date 27 6,472 Rittenhouse et a1. Apr. 24. 1883 591,204 Bittenbender Oct. 5, 1897 1,006,66l Knapp Oct. 24, 1911 2,141,880 Satre Dec, 27, 1938 2,330,933 ,Terrell,Jr. Oct. 5, 1943 2,463,353 Brown et a1. Mar. 1, 1949 

